Airbag module

ABSTRACT

An airbag module for a motor vehicle includes a gas sack that can be inflated with gas to protect an occupant, a gas generator for generating the gas provided for inflating the gas sack, and an additional cooling device comprising an openable reservoir for storing a coolant. The reservoir is opened when the gas sack is inflated, so that the coolant for cooling the gas used to inflate the gas sack can come into contact with the gas. The cooling device comprises a movement generating device that opens the reservoir to release the coolant.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of U.S. application Ser. No.12/230,545, filed Aug. 29, 2008, which is a continuation ofInternational Application PCT/EP2007/001872, which has an internationalfiling date of Mar. 5, 2007; this International Application was notpublished in English, but was published in German as WO 2007/101644. Theforegoing International application is incorporated herein by referencein its entirety.

BACKGROUND

The application relates to an airbag module for a motor vehicle. DE 19602 695 C2 (incorporated by reference herein) discloses a gas generatorhaving a cooling device that has a reservoir, for storing a coolingliquid, in the form of a cooling pouch made from a durable plastic film,that is damaged by hot gases provided by the gas generator and therebyreleases the coolant contained therein to cool the gas generated by thegas generator.

It would be advantageous to provide a cooling device including amovement generating device that opens the reservoir to release thecoolant with an improved adaptability to a person to be protected and arespective accident situation.

SUMMARY

One disclosed embodiment relates to an airbag module for a motorvehicle. The airbag module includes a gas sack that can be inflated withgas to protect an occupant, a gas generator for generating the gasprovided for inflating the gas sack, and an additional cooling devicecomprising an openable reservoir for storing a coolant. The reservoir isopened when the gas sack is inflated, so that the coolant for coolingthe gas used to inflate the gas sack can come into contact with the gas.The cooling device comprises a movement generating device that opens thereservoir to release the coolant.

Another embodiment relates to a method for restraining an occupant of amotor vehicle with an airbag module. The method includes inflating a gassack of the airbag module to protect the occupant, and releasing acoolant into an interior space of the gas sack with a cooling device ofthe airbag module to reduce the temperature prevailing in the interiorspace of the gas sack during inflating. The time of the release of thecoolant is calculated by an electronic control unit as a function of atleast one parameter from a sensor unit assigned to the airbag module.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory only,and are not restrictive of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the presentinvention will become apparent from the following description, appendedclaims, and the accompanying exemplary

FIG. 1 shows a schematic sectioned view of an airbag module having acooling device.

FIG. 2 shows a schematic sectioned view of a detail of the airbag moduleshown in FIG. 1.

FIG. 3 shows a schematic, sectioned detail view of a modification of theairbag module shown in FIGS. 1 and 2.

FIG. 4 shows a schematic, sectioned detail view of a furthermodification of the airbag module shown in FIGS. 1 to 3.

FIG. 5 shows a schematic sectioned view of a modification of the airbagmodule shown in FIGS. 1 and 2 with two separately actuable coolingdevices,

FIG. 6 shows a schematic sectioned view of a modification of the airbagmodule shown in FIG. 5, with the two cooling devices being assigneddifferent chambers of the gas sack.

FIG. 7 shows a schematic sectioned view of a further modification of theairbag module shown in FIGS. 5 and 6, with three separately triggerablecooling devices that are each assigned one chamber of the gas sack.

FIG. 8 shows a schematic sectioned view of an airbag module of the typeshown in FIGS. 1 and 2, with a cooling device that opens a dischargeopening of the gas sack.

FIG. 9 shows a plan view of a cooling device of the type shown in FIG.8, with a central nozzle for opening the discharge opening of the gassack.

FIG. 10 shows a schematic sectioned illustration of an embodiment of acooling device for an airbag module for reducing the gas internalpressure of a gas sack, with a piston for releasing a coolant driven bya pyrotechnic movement generating device.

FIG. 11 shows a schematic sectioned illustration of a modification ofthe cooling device shown in FIG. 10, with the coolant being acted onwith a gas via a diaphragm.

FIG. 12 shows a schematic sectioned illustration of a modification ofthe cooling device shown in FIG. 10, where the piston for pressurizingthe coolant is mounted in the reservoir by a rotatable threaded bar.

FIG. 13 shows a schematic sectioned illustration of a further embodimentof a cooling device for reducing the gas internal pressure of a gas sackincluding a pressurized coolant.

FIG. 14 shows a schematic sectioned illustration of a modification ofthe cooling device shown in FIG. 13 in which the coolant is pressurizedby a gas cushion provided in the reservoir.

FIG. 15 shows a perspective view of a cooling device that is integratedinto a diffuser.

FIG. 16 shows a sectioned detail view of the diffuser shown in FIG. 15,before the triggering of the cooling device.

FIG. 17 shows a sectioned detail view of the diffuser shown in FIG. 15,after the triggering of the cooling device.

FIG. 18 shows a modification of the diffuser shown in FIG. 15.

FIG. 19 shows a graphic illustration of the dependency of the gas sackinternal pressure on the quantity of introduced cooling fluid for acertain coolant and for three different gas sack volumes.

DESCRIPTION

It is possible for the temperature of the gas situated in the gas sackto be influenced by of the cooling device irrespective of the time ofactivation of the gas generator. Since the pressure prevailing in thegas sack is proportional to the temperature of the gas situated in thegas sack, it is thereby possible for the gas sack to be adapted to aperson to be protected or to a specific accident situation. It isthereby possible in certain scenarios, such as in a minor accident or alight person such as a 5% woman, for the cooling of the gas used toinflate the gas sack to take place relatively early so that the gas sackis inflated less intensely. In the event of a particularly heavyaccident or a very heavy person (50% to 95% man) it is possible for acooling of the gas to take place correspondingly late or not at all, sothat the gas sack is inflated to be correspondingly firm.

In a collision event, an out of position situation may occur, such aswhen an occupant to be protected by the gas sack is not sufficientlyremote from the gas sack in a main unfolding direction along which thegas sack moves towards the occupant during unfolding. In such asituation, it is also possible for the cooling of the gas situated inthe gas sack to take place early, so that the gas sack has a relativelylow pressure corresponding to the small spacing between the occupant andthe gas sack to reduce the chance of an occupant being injured duringunfolding.

The movement generating device preferably opens the reservoir at apredefinable time, with the time being calculated by an electroniccontrol unit as a function of at least one parameter that can bedetected by a sensor unit. The parameter can, for example, be the massof the occupant to be protected by the gas sack, a deceleration of thevehicle caused by an accident, a relative speed between the motorvehicle and a collision object that is colliding with the motor vehicle,or a spacing between the gas sack and an occupant in the main unfoldingdirection of the gas sack (e.g., the spatial position of the occupant inthe motor vehicle). It is also possible for the electronic control unitto evaluate a selection of the above parameters to determine a time ofthe activation of the cooling device.

The cooling device preferably opens a closure of an outflow opening ofthe reservoir with the movement generating device. The coolant can passthrough the open outflow opening into an interior space of the gas sack.The outflow opening is preferably arranged in the interior space of thegas sack. It is thereby advantageously possible for the coolant todistribute over a large volume in the interior space, and to providecorrespondingly effective cooling of the gas situated in the interiorspace of the gas sack within a very short time.

Before the release of the coolant, the outflow opening is closed off bythe closure. To open the closure, the movement generating devicepreferably provides a pressure that acts on the closure.

In an alternative embodiment, the closure is formed in one piece withthe reservoir, with it being possible for predetermined breaking pointsto be provided on the outflow opening that is closed off by the closure,so that the closure can be reproducibly detached from the reservoir bybeing acted on with pressure. Alternatively, the closure is preferablyadhesively bonded or welded to the outflow opening. The closure ispreferably embodied here as a film that covers the outflow opening thatcan be formed to be self-adherent to close off the outflow opening.Alternatively, the film for closing off the outflow opening can bemelted with an edge region of the outflow opening. In another exemplaryembodiment, the closure is embodied as a reversibly (non-destructively)openable valve.

The cooling device preferably provides an overpressure in the reservoirthat causes a release of coolant through the outflow opening of thereservoir when the outflow opening is open. Such an overpressure can,for example, be generated pyrotechnically or by a motor-driven punchthat presses against the coolant and thereby increases the pressureprevailing in the reservoir. The increased pressure in the reservoirfacilitates the releasing of the coolant and, if appropriate, theopening of the closure.

In addition, the cooling device preferably provides the overpressure forreleasing the coolant at a predefinable time in the reservoir, with thetime being calculated by the electronic control unit as a function of aselection of the above parameters.

The movement generating device preferably provides an overpressure inthe reservoir that both opens the closure of the outflow opening (torelease the coolant) and also presses the coolant through the outflowopening and out of the reservoir. A permanent overpressure may alsoprevail in the reservoir. In this case, the movement generating devicecan serve merely for the (controllable) opening of the closure of theoutflow opening of the reservoir. Here, the movement generating devicecan also be mechanically coupled to the closure to open the closure.

The cooling device preferably releases a predeterminable and variablequantity of coolant per unit time. The quantity of coolant to bereleased into the interior space of the gas sack per unit time can becalculated by an electronic control unit that, during a collision,continuously evaluates occupant-related parameters (e.g., the size ofthe occupant to be protected, the mass of the occupant or the positionof the occupant in relation to the unfolding gas sack, etc.) orvehicle-related parameters (e.g., speed of the motor vehicle, relativespeed with respect to the collision partner, deceleration of the motorvehicle during the collision, etc.) that are detected by a sensor unit.The electronic control unit converts the parameters into correspondingvalues for the coolant quantity to be released per unit time. The timeprofile of the quantity of coolant released into the gas sack per unittime is therefore controllable in real-time. The pressure that thecooling device exerts on the coolant can serve as the variable to becontrolled. According to one exemplary embodiment, The outlet has anarea aligned perpendicular to an outflow direction of the coolant,through which the coolant flows as it passes out of the reservoir, thatis constant. In the case of a constant outlet cross section, the coolantquantity released per unit time rises with increasing pressure. It isconversely possible, in the case of an approximately constant pressure,for the quantity of coolant to be released per unit time to be regulatedby varying the outlet cross section.

In the case of a liquid coolant, the droplet size can serve as a furtheradjusting variable for controlling the cooling action of the coolingdevice. The cooling effect is provided more quickly in the case ofcomparatively finely sprayed coolant (small droplets), on account of therelatively large effective surface of the coolant, than in the case ofcomparatively large droplets. The same applies to solid coolant (powderand foams). The droplet size can be influenced in particular by theshape of the outflow opening, in particular the outlet cross sectionthereof, and by varying the pressure that the coolant is under.

The above-described regulating mechanisms can of course also be combinedwith one another.

In an alternative embodiment, the coolant contained in the reservoir isunder a permanent pressure (that decreases when the outflow opening isopened) such that, when the closure of the outflow opening is opened,the coolant is released into the interior space of the gas sack. Oncereleased into the interior space of the gas sack, the coolant cools thegases introduced into the gas sack during inflating and reduces thepressure of the gases.

The coolant itself can be under pressure or a gas cushion in thereservoir may act (constantly) on the coolant via a piston to pressurizethe coolant.

If the coolant is pressurized, the quantity of coolant passing out ofthe reservoir per time interval is preferably controlled by an actuationof the closure of the outflow opening, (e.g., by a time-dependentvariation of the effective outlet cross section of the outflow opening).The closure of the outflow opening (as an element of a valve unit) ispreferably moveable in a reciprocating fashion between a first and asecond position, with the outflow opening being closed in the firstposition of the closure, and allowing a maximum quantity of coolant topass through per unit time in the second position. The closure canpreferably be arranged in at least one intermediate position that issituated between the first and second positions, so that the outflowopening can be opened and closed in a stepped fashion. A continuousmovement of the closure can preferably be performed via any desirednumber of lockable intermediate positions, so that the size of theoutlet cross section can be controlled precisely in a continuouslyvariable fashion. A movement between two positions, (e.g., between twodifferent intermediate positions) is brought about by the movementgenerating device.

In a further exemplary embodiment, the coolant is released after beingacted upon by a gas that is generated pyrotechnically by the movementgenerating device (gas generator).

The coolant is preferably enclosed in a diaphragm that, before beingacted on with gas, simultaneously functions as a closure of the outflowopening by sealingly enclosing the coolant and thereby preventing thecoolant from passing out through the outflow opening of the reservoir.The diaphragm is configured to be destroyed when acted upon by theimpulse exerted by the gas or by the inner energy of the gas, so thatthe overpressure (in relation to the pressure prevailing in the gassack) provided in the reservoir by the generated gas causes a release(outflow) of the coolant through the outflow opening of the reservoir.

Instead of a diaphragm, a piston moveable in the reservoir may transmitthe gas pressure to the coolant. The piston is acted on with a gas andmoves from a first position into a second position, with the secondposition corresponding to a volume of the reservoir that is reduced insize in relation to the first position (e.g., the coolant is pressed outof the reservoir by the piston).

In a further embodiment, the movement of the piston from the first intothe second position is provided not by a pyrotechnic device but ratherby a movement generating device, such as a motor that drives a rotatablethreaded bar. The piston is mounted to the threaded bar in thereservoir, so that the piston can, with a correspondingly directedrotation of the threaded bar, be moved continuously in a reciprocatingfashion between a first position and a second position. The coolant ispressurized by compression as the piston moves into the second position.In such a cooling device, it is possible to use both an irreversibleclosure (that can be opened by being destroyed) and also a reversibleclosure (that can be moved in a reciprocating fashion between twopositions) of the outflow opening.

The movement generating device preferably interacts with an electroniccontrol unit that triggers the movement generating device at apredeterminable time as a function of at least one parameter that can besensed by a sensor unit. The sensing of the parameter and thecalculation of the variable to be controlled (e.g., pressure of thecoolant as a function of the time, time of opening of the closurerelative to the time of activation of the gas sack, time duration duringwhich the closure is open, outlet cross section of the outflow openingas a function of the time, droplet or particle size of the coolant to bereleased, etc.) is preferably carried out in real-time during thecollision or during the inflating of the gas sack.

The coolant is preferably capable of flowing as it passes through theoutflow opening. In one alternative embodiment, the outflow openingconfigured to atomize the liquid coolant into a plurality of droplets asit flows out of the outflow opening into the interior space of the gassack. The coolant is preferably introduced into the interior space ofthe gas sack along an outflow direction that points toward the interiorspace. The outflow direction preferably runs along a main unfoldingdirection of the gas sack, along which an inflating gas sack movestoward an occupant to be protected. This ensures a particularly fastdistribution of the coolant in the interior space of the gas sack.

The coolant is preferably vaporized by the heat of the gas that is to becooled. It is possible here to obtain particularly effective cooling ofthe gas for inflating that is provided by the gas generator since thetransition of the coolant from the liquid into the gaseous phaseconstitutes a phase transition of the first type, in which the heat ofthe hot gas that is introduced into the interior space of the gas sackserves to drive the phase transition. The available heat of the hot gasat least partially causes the phase conversion of the coolant. Thereservoir together with the outflow opening projects at least insections into the interior space of the gas sack so that the coolant canbe effectively distributed in the interior space of the unfolding gassack by the cooling device.

However, the coolant need not strictly be in a purely liquid state ofaggregation as it is introduced into the gas sack. In an alternativevariant, the coolant is in a solid state of aggregation (for examplepowder or foam) when released, and is preferably finely atomized by thecooling device when released, with it being possible for the degree offineness (e.g., the droplet size of a liquid coolant) to be controlledby the cooling device. In addition, the coolant can also be in a gaseousstate of aggregation when released. In a further alternative embodiment,the coolant is a mixture that can contain gaseous, liquid and/or solidsubstances.

In a further exemplary embodiment, in addition to the time-dependentlycontrollable cooling of the gas used to inflate the gas sack, adischarge opening on the gas sack is provided, through which, in an openstate, gas can be discharged out of the gas sack. Before the inflationof the gas sack or before the activation of the cooling device, thedischarge opening is closed off by a diaphragm that is destroyed by theaction of the coolant. Here, the diaphragm can be destroyed (decomposed)by a mechanical action of the coolant and/or by a chemical action of thecoolant on the diaphragm.

In one embodiment, at least a part of the coolant is introduced into thegas sack as a jet that is directed at the diaphragm. The cooling devicepreferably has an additional nozzle that shapes the jet and can beformed on the reservoir adjacent to the outflow opening of thereservoir. If a plurality of outflow openings is provided, these can bearranged concentric to the (central) nozzle. The gas generatorpreferably has a flange for fastening the gas generator to a generatorsupport of the airbag module. The flange preferably protrudes from thegas generator and at least partially encircles the gas generator. Thegenerator support preferably forms a receptacle for the gas sack in afolded state having an openable cover that faces toward the driver (oranother occupant) when the airbag module is installed in a motorvehicle. The gas sack can unfold through the cover into an exteriorspace that surrounds the airbag module. The cover may have tear-offlines along which the cover tears off when, as a result of the gas beingintroduced into the gas sack, the gas sack expands along its mainunfolding direction and presses against the cover.

A base of the generator support extends transversely with respect to themain unfolding direction of the gas sack. The base is preferablysituated opposite the cover of the generator support along the mainunfolding direction of the gas sack. The base is connected to the coverby a wall that extends from the base of the generator support.

The base preferably has a central gas generator opening that receivesthe gas generator, with the gas generator opening having an encirclingedge region that is coupled to the flange of the gas generator.

The gas sack preferably has an inflow opening for introducing gas intothe interior space of the gas sack, with an edge region that encirclesthe inflow opening and fixes the gas sack to the generator support. Theedge region of the gas sack is clamped between the edge region of thegenerator opening and the flange of the gas generator. The gas generatorprojects along the main unfolding direction of the gas sack, through theinflow opening of the gas sack, into the interior space of the gas sack.

The flange is preferably connected to the base of the gas generator withat least one connecting element (e.g., a screw, a rivet, or a similarfastening mechanism) that extends longitudinally along a direction ofextent. The flange preferably has at least one first continuous cut-outthat is aligned with a second continuous cut-out that is formed at theedge region of the gas generator opening of the generator support. Theconnecting element is guided through the two aligned cut-outs of theflange and of the base of the generator support, and is suitably fixedthere so that a connection is produced between the flange and the baseof the generator support.

In an exemplary embodiment, the flange has at least one first continuousrecess, with the gas generator bearing with its flange on the edgeregion of the gas generator opening such that the first continuousrecess of the flange comes to rest on a second continuous recess of theedge region of the gas generator opening.

The reservoir of the cooling device is preferably inserted into the tworecesses such that the flange and the base of the generator supportencloses the reservoir in cross section.

In an alternative embodiment, the outflow opening of the reservoir ofthe cooling device is formed by a passage opening of the connectingelement. The outflow opening is aligned with the direction of extent ofthe connecting element. The connecting element guided through the twoaligned cut-outs of the flange and of the base of the generator supportserves as a nozzle of the cooling device through which the coolant canpass out of the reservoir. The connecting element includes an openableclosure of the above-described type, into the interior space of the gassack. The reservoir is preferably connected to the connecting element atan outer side of the base of the generator support that faces away fromthe interior space. A thread can be provided on a free end region of theconnecting element that projects into the exterior space of the airbagmodule. The thread on the connecting element engages a correspondingthread on the reservoir. In addition, the reservoir can also beconnected to the connecting element with a plug-type connection. It isalso possible for the reservoir to be adhesively bonded or welded to theconnecting element. This variant of the cooling device is advantageousbecause it makes it particularly simple for an airbag module to beretrofitted with a cooling device. It is merely necessary for the oneconnecting element (or one of a plurality of connecting elements) to beremoved from their installed position and to be exchanged for aconnecting element provided with the passage opening.

In a further exemplary embodiment, the reservoir is spaced apart fromthe other components of the airbag module in a motor vehicle, with themovement generating device being integrated into the reservoir. Aninflow line connects the reservoir to a connecting element with anoutflow opening so that the coolant can pass via the inflow line intothe gas sack. The inflow line is arranged in the interior space of thegas sack or in the interior space of the airbag module.

In an alternative exemplary embodiment, the cooling device is integratedinto the gas generator. The cooling device is preferably arrangedcentrally in an upper side of the gas generator facing towards theinterior space such that the reservoir of the cooling device issurrounded at least in sections by the gas generator. The outflowopening of the reservoir faces toward the interior space of the gas sackalong the main unfolding direction. This advantageously provides asymmetrical design of the cooling-device/gas-generator unit that ensuresspatially highly uniform cooling of the gas situated in the gas sack.

The airbag module preferably has a diffuser for distributing the gasesused by the gas generator to inflate the gas sack. The diffuser projectsthrough an inflow opening of the gas sack into the interior space of thegas sack and preferably serves to clamp an edge region of the gas sackto a part of the airbag module. The part can in particular be a flangeof the gas generator or a generator support.

The diffuser has a flange that annularly encircles the diffuser in aperipheral direction aligned in particular transversely with respect tothe main unfolding direction of the gas sack. The flange helps to couplethe diffuser to the airbag module and to clamp the gas sack to theairbag module. According to one embodiment, the reservoir is of (open)annular design and can preferably be detachably fastened to thediffuser, with the reservoir encircling on the flange of the diffuseralong the peripheral direction of the flange.

The annular reservoir has a first end section on which a plurality ofoutflow openings for releasing the coolant are formed on an upper sidethat faces toward an interior space of the gas sack of the reservoir anda second end section that is situated opposite the first end sectionalong the peripheral direction.

A piston for releasing the coolant is mounted in the second end sectionof the reservoir, with the piston being moveable along the peripheraldirection. The piston is moveable from a first to a second position inwhich the piston is arranged closer to the first end section of thereservoir along the peripheral direction. The coolant that is stored inthe reservoir can therefore be pressed out of the reservoir by amovement of the piston from the first into the second position. Thedrive of the piston is preferably provided by a pyrotechnic movementgenerating device that acts on the piston with gas to move the pistonfrom the first into the second position.

In one alternative embodiment, the cooling device that is provided onthe diffuser has a pressure chamber that interacts with the reservoir.The cooling device adjoins and extends along the reservoir and can befilled with gas to pressurize the coolant. The pressure chamber and thereservoir are preferably separated from one another by a diaphragm sothat a pressure increase in the pressure chamber can be transmitted viathe diaphragm to the coolant situated in the reservoir. The diaphragmmay be acted upon by a gas and be moved from a first position into asecond position, with the diaphragm pressing the coolant that issituated in the reservoir out of the reservoir during the movement fromthe first into the second position. Alternatively, the diaphragm can bedestroyed so that the coolant is acted on directly by the gases. Thecoolant passes out of the reservoir through the outflow openings thatare preferably distributed uniformly along the peripheral direction onan upper side of the reservoir facing toward the interior space of thegas sack.

In one alternative embodiment, the reservoir and/or the pressure chamberare formed in one piece with the flange of the diffuser.

Alternatively, the cooling device can form a separate sub-module thatcan be fastened to the diffuser, so that a conventional diffuser can beretrofitted with a cooling device as described herein. The sub-modulemay comprise at least the reservoir, if appropriate the pressure chamberthat is connected via the diaphragm to the reservoir, and the movementgenerating device (if appropriate with piston). In addition, thesub-module can also contain the electronic control unit for actuatingthe cooling device. The sub-module may be coupled to the (vehicle-side)sensor unit with any suitable mechanism.

A further embodiment provides that a plurality of cooling devices areprovided. The cooling devices each include a reservoir for storing acoolant, with the respective reservoir opening when the gas sack isinflated, so that the coolant for cooling the gas used to inflate thegas sack can come into contact with the gas.

When using pyrotechnic movement generating devices for acting on thecoolant with a plurality of cooling devices, there is also thepossibility of controlling the time profile of the cooling in arelatively simple way (e.g., by activating the individual coolingdevices at defined (different) times to release coolants). It ispossible for the overall quantity of the coolant released per unit timeto be varied in that the individual cooling devices release a differentquantity of coolant. For example, different quantities of coolants maybe stored in the individual reservoirs, or a different number of coolingdevices may be activated.

In addition, the use of a plurality of cooling devices permitstime-differentiated and space-differentiated cooling of the gas situatedin the gas sack. The cooling devices are preferably assigned differentregions of the gas sack. The region can also be a separate gas sackchamber of the gas sack. This makes it possible to adapt the gas sackinternal pressure in a targeted fashion. It is thereby possible for thegas sack internal pressure prevailing in a central gas sack chamber,that forms an impact face for a head of an occupant, to be reduced in atargeted fashion to reduce the risk of injury to the occupant in thefacial region, while the gas sack chambers surrounding the central gassack chamber can be inflated to be considerably firmer to support thecentral gas sack chamber.

The individual cooling devices preferably interact with an electroniccontrol unit that activates the individual cooling devices separately(e.g., one after the other in time) to release coolants as a function ofat least one parameter that can be sensed by a sensor unit (e.g., size,mass, position of the occupant to be protected; speed, relative speed,deceleration of the motor vehicle during a collision, etc.).

It is preferable to reduce the gas sack internal pressure, for between0.05 g and 0.15 g of coolant per liter gas sack volume to be introducedinto the gas sack. This provides a pressure reduction in the region of10 kPa. Reducing the internal pressure facilitates the cooling of thegas introduced into the gas sack when the gas sack is inflated.

The cooling device can also be used in combination with further devicesthat likewise serve to adapt the gas sack to different crash conditions,for example by controlling the gas pressure prevailing in the gas sack.Such devices can for example be controllable discharge openings that canbe opened as a function of the respective accident situation, so thatgas can escape from the gas sack into an exterior space that surroundsthe airbag module. The time of opening and if appropriate the timeduration of the open state of a discharge opening can be calculated bysuitable control electronics as a function of a selection of the abovedescribed parameters. It is of course also possible for gas supplylines, that serve to introduce gas into the gas sack, to additionally becontrollable (for example closable).

According to one exemplary embodiment, a method for restraining anoccupant of a motor vehicle by an airbag module comprises inflating agas sack of the airbag module to protect the occupant fromcollision-related forces, detecting at least one occupant-related orvehicle-related parameter with a sensor unit, and releasing a coolantfrom an additional cooling device of the airbag module to reduce apressure prevailing in the gas sack during inflating. The time of therelease of the coolant is calculated by an electronic control unit as afunction of at least one parameter. The parameters define the positionand/or the variation with time of the position of the occupant to beprotected or of a vehicle that is involved in the collision and areobtained by the sensor unit.

The release of the coolant can take place at any desired time, inparticular also when a gas sack is only partially inflated.

The at least one parameter is preferably detected during a collision,with the time preferably being calculated during the collision (as thegas sack is inflated) in real-time. Alternatively or in addition tothis, the at least one parameter can be detected before the collision bya pre-crash sensor arrangement (sensor arrangement for detectingimpending collisions). Times or profiles for the activation of thecooling device can then be calculated by a control unit before thecollision or read out from a memory of the control unit.

If further control variables (such as for example the pressure of thecoolant or the outlet cross section of the outflow openings of areservoir) of the cooling device are controlled during the inflating ofthe gas sack, the at least one parameter is sensed multiple times duringa collision, so that the time profile of the control variables can beadapted to the present value of the at least one parameter or controlledcorresponding to the present value. The parameter can likewise becalculated multiple times already before the collision.

A plurality of the above-stated occupant-related and/or vehicle-relatedparameters can be detected by the sensor unit (or a plurality of sensorunits).

The coolant is preferably introduced into the gas sack during a timespanwith a duration that is calculated by the electronic control unit,preferably before or during the collision, as a function of at least oneparameter that is detected by the sensor unit.

To be able to adapt the time profile of the pressure prevailing in thegas sack precisely to the respective accident situation, a variablequantity of coolant is released per unit time, with the quantity ofcoolant that is introduced into the gas sack per unit time beingcalculated by the control unit, preferably before or during thecollision, as a function of the at least one parameter.

The coolant is preferably, to control the quantity of coolant to bereleased per unit time, subjected to a variable pressure. In the case ofa high pressure, a larger quantity passes out of the reservoir per unittime when the outflow openings are open than at a comparatively lowpressure. The magnitude of the pressure applied to the coolant iscalculated by the control unit, preferably before or during thecollision, as a function of the at least one parameter.

One variant of the disclosed method provides that the coolant isfragmented into individual particles of predeterminable volume whenreleased, with the (average) volume of the particles to be set beingcalculated by the control unit, preferably before or during thecollision, as a function of the at least one parameter. If the coolingdevice sets the particle volume by varying the outlet cross section ofthe at least one outflow opening, the control unit converts theparameter into an outlet cross section, to be set, of the at least oneoutflow opening.

A particle is to be understood here to mean a unit of coolant (droplet,grain, etc) that coheres when the coolant is released.

In another variant of the method, it is provided that, to reduce thepressure prevailing in the gas sack during inflating, a plurality ofcooling devices are activated, with a predeterminable coolant quantitybeing introduced into the gas sack at a predeterminable time by each ofthe cooling devices. The respective times of the release of the coolantrelative to the start of unfolding of the gas sack are preferablycalculated here by the electronic control unit, preferably before orduring the course of the accident (for example collision), as a functionof the at least one parameter. The parameter is if appropriate detectedby a sensor unit multiple times during the course of the accident orduring the inflating of the gas sack.

In a further embodiment of the method, it is provided that the at leastone cooling device is actuated as a function of at least one additionalrestraint device, in particular as a function of a belt force limiterfor limiting the crash-related forces introduced into an occupant by abelt in the event of a crash. A sensor unit can detect belt-specificparameters (belt extraction, speed of belt extraction), with anelectronic control unit using parameters for controlling the coolingdevice. It is thus for example possible, in the event of an alreadycomparatively large belt extraction at the time of activation of the gassack, to conclude that the occupant is positioned too close to the gassack. The electronic control device classifies the belt elongation andto initiate cooling of the gases situated in the gas sack by triggeringthe cooling device at a correspondingly early time.

FIGS. 1 and 2 show schematic sectioned views of an airbag module 1 thathas a gas sack 2 that can be inflated to protect a person, and a gasgenerator 3 that provides the gas required to inflate the gas sack 2.The gas generator 3 has an igniter 3 a that can be actuated byvehicle-side control electronics. The gas sack 2 and the gas generator 3of the airbag module 1 are fixed to a generator support 4 together witha cooling device 5 that is arranged adjacent to the gas generator 3 andcools the gas used to inflate the gas sack 2. The airbag module 1 shownin FIG. 1 and FIG. 2 is an airbag module 1 for assembly in the steeringwheel of a motor vehicle. With corresponding design of the individualcomponents, however, the airbag module 1 may also be arranged at anotherpoint on the motor vehicle and used to protect an occupant (e.g., avehicle dashboard, a side column, a seat cushion, etc.). The sectionplane of the airbag module 1 shown in FIG. 1 runs parallel to a steeringaxis of the steering wheel (not shown).

The generator support 4 has a cover through which the gas sack 2, thatis illustrated in FIG. 1 in an inflated state, can unfold into anexterior space A that surrounds the airbag module 1, specifically alonga main unfolding direction H that runs parallel to the steering axis. Abase 6 of the generator support 4 is situated opposite the cover of thegenerator support 4 counter to the main unfolding direction H. The base6 is connected to the cover (not shown) of the generator support 4 by awall 7 that projects from the base 6 along the main unfolding directionH. The base 6 has a central, continuous gas generator opening 8, with anencircling edge region 9 that borders the gas generator opening 8 and onwhich a flange 10 of the gas generator 3 bears. The flange 10 encirclesthe gas generator 3 transversely with respect to the main unfoldingdirection H and fastens the gas generator 3 to the edge region 9 of thegas generator opening 8. The flange 10 is formed here to be of planarannular design, so that it contacts the edge region 9 of the gasgenerator opening 8.

The gas sack 2 has an inflow opening through which gas can be conductedinto an interior space I of the gas sack 2 to inflate the gas sack 2. Tofix the gas sack 2 to an inner side of the base 6 of the generatorsupport 4 that faces toward the gas sack 2, an encircling edge region 11of the inflow opening of the gas sack 2 is clamped along the mainunfolding direction H between the edge region 9 of the gas generatoropening 8 and the flange 10 of the gas generator 3. In this way, the gasgenerator 3 projects into the interior space I of the gas sack 2 alongthe main unfolding direction H through the inflow opening of the gassack 2.

The flange 10 is connected to the edge region 9 of the gas generatoropening 8 by longitudinally extending connecting elements 12. Firstcut-outs 10 b are provided on the flange 10 and second cut-outs 6 a areprovided on the edge region 9 of the gas generator opening 8. Thecut-outs 6 a are aligned with one of the first cut-outs 10 b, with theconnecting elements 12 being inserted into the aligned first and secondcut-outs 10 b, 6 a to extend longitudinally along the main unfoldingdirection H.

The longitudinally extending connecting elements 12 have a widened head12 a that bears on the inner side 10 a, that faces towards the gas sack2, of the flange 10, and specifically on an edge region of the innerside 10 a that borders the respective first cut-out 10 b. Proceedingfrom an outer side of the base 6 that faces away from the gas sack 2,the free end regions of the connecting elements 12 that project awayfrom the base 6 can be coupled to nuts, so that a stable connection isproduced between the gas generator 3 and the generator support 4. Theflange 10 of the gas generator 3 is pressed against the edge region 9 ofthe gas generator opening 8 along the main unfolding direction H, withthe edge region 11 of the inflow opening of the gas sack 2 being clampedbetween the flange 10 and the edge region 9 of the gas generator opening8. Alternatively, the connecting elements 12 can also be embodied asrivets or can be fixed to the outer side of the base 6 that faces awayfrom the gas sack 2.

The cooling device 5 comprises a reservoir 5 a for storing a liquidcoolant K that can pass through an outflow opening 5 b into the interiorspace I of the gas sack 2. The outflow opening 5 b is formed here in themanner of a nozzle, so that the coolant K is atomized or fractioned intosmall droplets as it is introduced from the reservoir 5 a through theoutflow opening 5 b into the interior space I of the gas sack 2. Topress the coolant K out of the reservoir 5 a of the cooling device 5,the cooling device has a movement generating device 5 c that can beactivated by vehicle-side control electronics. The movement generatingdevice 5 c provides an overpressure in the reservoir 5 a that pressesthe coolant K against a closure V of the outflow opening 5 b. Theclosure V is opened by the overpressure provided in the reservoir 5 a bythe movement generating device 5 c, so that the coolant K is releasedthrough the outflow opening 5 b into the interior space I of the gassack 2 along the outflow direction R. The closure V of the outflowopening 5 b can be formed here in one piece with the reservoir 5 a ofthe cooling device 5, and tear open as a result of the overpressure. Itis likewise possible for a reversibly openable and closable valve to beused as a closure V of the outflow opening 5 b. The valve can beactuated independently of the movement generating device 5 c to open theoutflow opening 5 b. It is essential that the activation of the coolingdevice 5 can take place completely independently of the activation ofthe gas generator 3. Here, a time of activation of the cooling device 5can be calculated by a suitable electronic control unit as a function ofa specific accident situation. In the case of a reversibly openable andclosable closure V of the outflow opening 5 b, it is likewiseconceivable that, to meter the coolant K with the electronic controlunit, a timespan is calculated during which the coolant K is releasedthrough the outflow opening 5 b into the interior space I of the gassack 2. An overpressure in the reservoir 5 a that conveys the coolant Kinto the interior space I of the gas sack 2, can be provided by areversibly operating movement generating device, for example by amotor-driven punch that presses against the liquid coolant K along theoutflow direction R.

Since, for a constant volume, the pressure of the gas situated in thegas sack 2 is proportional to the temperature of the gas, the coolingcauses a reduction of the gas pressure prevailing in the gas sack 2. Thegas sack 2 can be adapted to a specific accident situation with thecontrollable cooling of the gas situated in the gas sack 2. Earlycooling of the gas (reduction of the gas pressure) can for example takeplace if a driver is at too small a distance from the gas sack (out ofposition) along the main unfolding direction H of the gas sack 2.

A first recess 10 c is provided on the flange 10 of the gas generator 3and a second recess 6 b is provided on the edge region 9 of the gasgenerator opening 8 to fasten the cooling device 5 to the airbag module1. The recesses are substantially congruent and aligned with oneanother. The cooling device 5 is inserted into the aligned recesses 10c, 6 b so that the flange 10 and the edge region 9 of the gas generatoropening 8 enclose the reservoir 5 a of the cooling device 5 in crosssection.

To fix the cooling device 5 to the two recesses that are aligned withone another, the cooling device 5 has a conically shaped head 5 d thatis widened at its base, surrounds the outflow opening 5 b and bears onan edge region, that borders the first recess 10 c of the flange 10, ofthe inner side 10 a of the flange 10. Proceeding from the outer side,that faces away from the interior space I, of the base 6, the coolingdevice 5 is screwed to the base 6 and to the flange 10 of the gasgenerator 3 with a nut 5 e that engages around the reservoir 5 a of thecooling device 5 in cross section. The cooling device 5 can of coursealso be fixed to the base 6 and to the flange 10 in some other knownway.

The outflow opening 5 b of the cooling device 5 is formed on thereservoir 5 a in particular such that the outflow direction R, alongwhich the liquid coolant K is released into the interior space I of thegas sack 2, runs substantially parallel to the main unfolding directionH of the gas sack 2. The cooling effect is provided in that the coolantK is atomized and vaporized by the hot gas situated in the interiorspace I, with the temperature of the gas being lowered, since energymust be expended in converting the liquid phase of the coolant into thegaseous phase.

FIG. 3 shows a modification of the airbag module 1 shown in FIGS. 1 and2. Here, in contrast to the cooling device 5 of FIGS. 1 and 2, thehousing of the cooling device 5 is formed by a connecting element 13(corresponding to the connecting element 12 of FIG. 2) and a reservoir 5a that, proceeding from an outer side of the base 6, is connected to afree end region 13 b of the connecting element 13 that projects from theouter side of the base 6 counter to the main unfolding direction H. Thereservoir 5 a has an outflow opening 5 f that, before an activation ofthe cooling device 5, is closed off by the closure V that can beembodied as per FIG. 2. Additionally formed on the connecting element 13in contrast to the connecting element 12 of FIG. 2 is a passage opening13 c that extends along the main unfolding direction H and connects theinterior space I of the gas sack 2 to the reservoir 5 a of the coolingdevice 5 via the outflow opening 5 f.

The reservoir 5 a of the cooling device 5 can be connected to the freeend region 13 b of the connecting element 13 that projects from theouter side of the base 6 in particular with a screw connection betweenthe free end region 13 b and the reservoir 5 a. The free end region 13 bhas a thread that engages into a thread of the reservoir 5 a at acut-out of the reservoir 5 a. According to various embodiments, thereservoir 5 a can be adhesively bonded, clamped or welded to the freeend 13 b of the connecting element 13.

FIG. 4 shows a further modification of the airbag module 1 shown inFIGS. 1 to 3, in which, in contrast to FIGS. 1 to 3, the cooling device5 is arranged not partially in the exterior space A of the airbag module1 but rather completely within the interior space I of the airbag module1 or of the gas sack 2. A recess is provided on an upper side 3 b of thegas generator 3 into which the cooling device 5 is fully integrated, sothat the reservoir 5 a of the cooling device 5 is surrounded in crosssection by the gas generator 3 with the exception of the head 5 d of thecooling device 5. The widened head 5 d of the cooling device 5 bears onan edge region of the upper side 3 b of the gas generator 3. The edgeregion borders the recess in which the cooling device 5 is inserted in aform-fitting manner. The advantage of such an arrangement of the coolingdevice 5 on the gas generator 3 is in the shaping of the cooling device5/gas generator 3 unit that is rotationally symmetrical with respect tothe main unfolding direction H. The symmetry facilitates thetransversely uniform cooling of the gas with respect to the mainunfolding direction H. The outflow opening 5 b of the cooling device 5here faces toward the interior space I of the gas sack 2 along the mainunfolding direction H.

FIG. 5 shows a schematic sectioned view of a modification of the airbagmodule 1 shown in FIGS. 1 and 2. In contrast to FIGS. 1 and 2, anadditional second cooling device 5 is provided. To fasten the additionalcooling device 5 to the airbag module 1, a further first recess 10 c isprovided on the flange 10 of the gas generator 3, and a further secondrecess 6 b is provided on the edge region 9 of the gas generator opening8. The recesses are substantially congruent and aligned with oneanother. The cooling device 5 is, as illustrated in FIG. 2, insertedinto the recesses 10 c, 6 b so that the flange 10 and the edge region 9of the gas generator opening 8 likewise enclose the reservoir 5 a of thefurther cooling device 5 in cross section. The additional cooling device5 is situated opposite the other cooling device 5 transversely withrespect to the main unfolding direction H so that the gas generator 3 isarranged between the two gas generators 5. Different regions 22, 23 ofthe gas sack 2 can be cooled independently of one another by the twocooling devices 5. The two regions 22, 23 can for example be aright-hand and a left-hand gas sack half 22, 23 of the gas sack 2. It isthereby possible, in the event of a frontal crash with a lateralcomponent, to provide a pressure profile in the gas sack 2 correspondingto the side component of the collision by local cooling of theright-hand or left-hand gas sack halves 22, 23.

In addition, it is possible to provide a stepped reduction of the gassack internal pressures with time-offset triggering of the two coolingdevices.

FIG. 6 shows a modification of the airbag module 1 shown in FIG. 5,wherein, in contrast to FIG. 5, the right-hand and left-hand gas sackhalves 22, 23 form gas sack chambers that are separated from oneanother, with each gas sack chamber 22, 23 being assigned one of the twocooling devices 5, so that the gas sack internal pressure prevailing inthe interior spaces I of the two gas sack chambers 22, 23 can be setindependently of one another.

FIG. 7 shows a further modification of the airbag module 1 illustratedin FIG. 6, wherein, in contrast to FIG. 6, a central gas sack chamber 24that extends along the main unfolding direction H is provided. Thecentral gas sack chamber 24 is arranged between the right-hand andleft-hand gas sack chambers 22, 23 transversely with respect to the mainunfolding direction H. The central gas sack chamber 24 forms, at a sidefacing toward a driver F, an impact face for the head of the driver F(occupant). To control the gas internal pressure of the central gas sackchamber 24 of the gas sack 2, a cooling device 5 of the type of FIG. 4is provided. The cooling device 5 is integrated into the upper side 3 bof the gas generator 3 facing toward the occupant F and conveys thecoolant K along an outflow direction R that coincides with the mainunfolding direction H of the gas sack 2.

FIG. 8 shows a schematic sectioned view of a modification of the airbagmodule 1 shown in FIGS. 1 and 2, wherein, in contrast to FIGS. 1 and 2,the cooling device 5 generates a bundled coolant jet 60 to destroy adiaphragm 55 that is fixed to the gas sack 2 and covers (from thedirection of the exterior or interior space I) a discharge opening 50 ofthe gas sack 2. The discharge opening 50 can thereby be opened in atime-dependent fashion by the cooling device 5 to ventilate the gas sack2 (for example in the event of an out of position situation). Here, thejet 60 of the coolant K that is used can be formed such that thediaphragm 55 is destroyed mechanically (e.g., torn). Alternatively, thecoolant K can form a solvent for the diaphragm 55, so that the diaphragm55 is decomposed (e.g., dissolved) by the coolant once the coolant Kcomes into contact with the diaphragm 55.

In addition, in contrast to FIGS. 1 and 2, the longitudinal axis, thatcoincides with the outflow direction R, of the cooling device 5 isinclined in relation to the main unfolding direction H, so that the jet60 can impact against a diaphragm 55 that is provided laterally on thegas sack 2. To form the jet 60, the cooling device 5 has a centralnozzle 65 whose outlet cross section is formed to be larger than thoseof the other outflow openings 5 b of the cooling device 5, that servemerely to release the coolant K. The outflow openings 5 b are preferablyarranged along a circle that encircles the central nozzle 65, so thatthe coolant K can be introduced into the interior space I of the gassack 2 cylinder-symmetrically with respect to the jet 60.

FIG. 10 shows a schematic side view of a cooling device 5 of the typeshown in FIGS. 1 to 9, having a reservoir 5 a in which a liquid coolantis stored. The coolant is introduced into the interior space I of thegas sack 2 as the gas sack 2 is inflated to reduce the gas internalpressure of the gas sack 2. The reservoir 5 a of the cooling device 5has a cylindrical wall with a longitudinal axis that runs along the mainunfolding direction H. The reservoir 5 a has a conically tapering head 5d with duct-like outflow openings 5 b that, adjacent to the wall, areinclined relative to the main unfolding direction H, so that the coolantK can be sprayed into the interior space I of the gas sack 2 at acorrespondingly large solid angle around the outflow direction R thatcoincides with the main unfolding direction H.

A piston 20 is mounted, in a section of the reservoir 5 a that issituated opposite the head 5 d along the longitudinal axis of thereservoir 5 a, to be moveable along the longitudinal axis of thereservoir 5 a. As the piston 20 moves in the direction of the head 5 dof the reservoir 5 a, it presses the coolant K that is stored in thereservoir 5 a through the outflow openings 5 b into the interior space Iof the gas sack 2, with the outflow openings 5 b of the reservoir 5 abeing dimensioned such that the coolant K is atomized into fine dropletsas it leaves the reservoir 5 a. To seal the reservoir 5 a, the piston 20preferably includes an encircling, outer edge region that bearssealingly against the wall of the reservoir 5 a.

The piston 20 is moved from its initial first position into its secondposition situated closer to the head 5 d by a movement generating device5 c that acts, with a pyrotechnically generated gas, on the side of thepiston 20 facing away from the head 5 d.

Before the release of the coolant K, the outflow openings 5 b can beclosed off individually or together by a film. Such a film can beprovided on the reservoir 5 a at the inside or at the outside. The timeat which the piston 20 is acted on with a gas (relative to the startingtime of the unfolding of the gas sack) is calculated here by anelectronic control unit S that is coupled to the movement generatingdevice 5 c. According to one embodiment, the time at which the piston 20is acted upon is calculated as a function of the specifiedoccupant-related or vehicle-related parameters. The calculation of thetime takes place in real-time. It is also possible for sensor units S′in the form of pre-crash detectors (e.g., detectors that detect animpending collision that has not yet begun) to be used to detect thestated parameters.

FIG. 11 shows a schematic sectioned view of a modification of thecooling device 5 shown in FIG. 10, wherein in contrast to FIG. 10, nopiston 20 is provided, but the coolant K is, before the triggering ofthe movement generating device 5 c, enclosed in a destructible casing inthe form of a diaphragm 30. When acted on with the gas provided by themovement generating device 5 c, the diaphragm 30 is destroyed and thecoolant K is pressed out of the reservoir 5 a by the gas pressuregenerated in the reservoir 5 a by the movement generating device 5 c.

FIG. 12 shows a schematic sectioned view of a modification of thecooling device 5 shown in FIGS. 10 and 11, in which the piston 20 ismounted with a motor-driven threaded bar 25 to be movable continuouslyin a reciprocating fashion between a first and a second position in thereservoir 5 a. The threaded bar 25 projects from a side facing away fromthe head 5 d of the piston 20, counter to the main unfolding direction H(e.g., along the longitudinal axis of the reservoir 5 a). The threadedbar 25 engages a corresponding threaded central recess 26 in a base 27of the reservoir 5 a. The threaded bar 25 is moved toward or away fromthe outflow openings 5 b as it rotates about its longitudinal axis(e.g., along the main unfolding direction H). Accordingly, the piston 20that is connected to the threaded bar 25 is moved in a reciprocatingfashion in the reservoir 5 a along the longitudinal axis of thereservoir 5 a or of the threaded bar 25. The threaded bar 25 ispreferably coupled to a movement generating device 5 c in the form of amotor that rotates the threaded bar 25 about its rotational axis to movethe piston 20 and release a defined amount of the coolant K.

The movement generating device 5 c is coupled, corresponding to FIGS. 10and 11, to an electronic control unit S that actuates the movementgenerating device 5 c as a function of at least one parameter that canbe detected by a sensor unit S′ that is coupled to the control unit S.The sensor unit S′ detects the at least one parameter multiple times,preferably at regular intervals, during a collision, so that thepressure acting on the coolant K can be controlled to release a definedamount of the coolant K, in real-time by the electronic control unit Sthat interacts with the movement generating device 5 c.

FIG. 13 shows a schematic sectioned view of a further embodiment of acooling device 5, in which, in contrast to FIGS. 10 to 12, the coolant Kitself is pressurized. To release the coolant K, a closure V may beopened by a movement generating device 5 c. The closure V preferablybeing continuously openable, and the outlet cross section of the outflowopenings 5 b can preferably be varied continuously by the closure V.

To control the outlet cross section of the outflow openings 5 b as afunction of at least one of the above-specified relevantoccupant-related and vehicle-related parameters, the (reversiblyworking) movement generating device 5 c is coupled to an electroniccontrol unit S that calculates, as a function of the at least oneparameter that is detected by the sensor unit S′ that is coupled to thecontrol unit S, the time at which and the time duration for which theclosure V is opened, and actuates the movement generating device 5 ccorrespondingly.

FIG. 14 shows a schematic sectioned view of a modification of thecooling device 5 shown in FIG. 13, wherein in contrast to FIG. 13, thecoolant K is not itself under pressure, but rather is acted on by a gascushion P that is provided in the reservoir 5 a and acts on the coolantK via a piston 20.

FIG. 15 shows, in connection with FIGS. 16 and 17, a cap-shaped diffuser70 that projects into the interior space I of the gas sack 2 through theinflow opening of the gas sack 2 along the main unfolding direction H. Aplurality of throughflow openings 71 are provided on the diffuser 70,through which throughflow openings 71 the gas generated by the gasgenerator 3 for inflating the gas sack 2 can flow into the interiorspace I of the gas sack 2. To fix the diffuser 70 to an encirclingflange 10 of the gas generator 3 (corresponding to FIGS. 1 to 4), thediffuser 70 itself has a flange 75 that can be fixed to the flange 10 ofthe gas generator 3 and that encircles the diffuser 70 along aperipheral direction U that is aligned transversely with respect to themain unfolding direction H. An edge region 2 a, that encircles theinflow opening of the gas sack 2, of the gas sack 2 is preferablyclamped, to fix the gas sack 2 to the airbag module 1, between theflange 10 of the gas generator 3 and the flange 75 of the diffuser 70.

Pins B project from the flange 75 of the diffuser 70 counter to the mainunfolding direction. The diffuser 70 can be fastened to a part of theairbag module 1 with pins B, in particular to a generator support 4. Inaddition, the pins B can serve to fasten the entire airbag module 1 to amotor vehicle part.

The flange 75 of the diffuser includes two (shell-like) elements 91, 92,annularly encircling the diffuser, that bear against one another. Withrespect to the main unfolding direction H, flange includes one upperelement 92 and one lower element 91. The two elements 91, 92 havecongruent recesses at sides 91 a, 92 a that face one another and withwhich said elements bear against one another. The recesses each encirclethe diffuser 70 along the peripheral direction U so that the twoelements 91, 92 form or delimit an annular chamber.

The chamber is divided by a diaphragm 30, with the—with respect to themain unfolding direction H—upper region, that encircles the diffuser 70,of the chamber forming a reservoir 5 a for a coolant K, and the lowerencircling region of the chamber, that is separated from the reservoir 5a by the diaphragm 30, forming a pressure chamber 90 that can be filledwith gas. To release the coolant K, the upper element 92 has, on a upperside 92 b that faces toward the interior space I of the gas sack 2, aplurality of outflow openings 5 b that are arranged uniformly along theperipheral direction U on the upper side 92 b, and that can be closedoff by a film, that is adhesively bonded to the upper side 92 b, beforea triggering of the cooling device K. In addition, a filling opening 5 gis provided on the upper side 92 b through which the reservoir 5 a canbe filled with a coolant K.

To fill the pressure chamber 90 with a gas, the cooling device 5 has amovement generating device 5 c in the form of a longitudinally extendinggas generator. The gas generator includes a longitudinal axis that ispreferably aligned along the main unfolding direction H. As the gasfills the pressure chamber 90, the diaphragm 30 is moved along the mainunfolding direction H in the direction of the reservoir 5 a (cf. FIG.17) and presses the coolant K out of the outflow openings 5 b. Themovement generating device 5 c is, corresponding to FIGS. 10 and 11,coupled to an electronic control unit S that actuates the movementgenerating device 5 c as a function of at least one occupant-related orvehicle-related parameter that is detected by a sensor unit S′.

The diaphragm 30 can be fixedly clamped between the two elements 91, 92that bear against one another, and thereby provide sealing of thechamber (reservoir 5 a and pressure chamber 90). One of the twoelements, for example the lower element 91, is preferably fixed to thediffuser 70 or integrally formed with the diffuser 70, while the upperelement 92 is fixed to the lower element 91. Here, the upper element 92may be screwed or crimped to the lower element 91 (if appropriate withthe interposition of the diaphragm 30) to form the reservoir 5 a and thepressure chamber 90.

FIG. 18 shows a perspective view of a modification of the cooling device5 shown in FIGS. 15 to 17. Here, the reservoir 5 a is preferably ofannular design and arranged around the diffuser 70 along the peripheraldirection U, with it being possible for the reservoir 5 a to bedetachably or fixedly connected to the flange 75 of the diffuser 70 (forexample by crimping). The reservoir 5 a has a first and a second endsection 80, 81 that are situated opposite one another along theperipheral direction U. Provided on the upper side, that faces towardthe interior space I of the gas sack 2, of the first end section 80 area plurality of outflow openings 5 b that, before the activation of thecooling device, can be closed off for example by a film. In theopposite, second end section 81, a piston 20 that seals off thereservoir 5 a is mounted to be moveable along the peripheral directionU. To seal off the reservoir 5 a, the piston 20 preferably bearssealingly against the wall of the reservoir 5 a. The piston 20 can havean elastic outer edge region (for example made from a rubber). Torelease the coolant K stored in the reservoir 5 a, the piston 20 can beacted on, at a side that faces away from the reservoir 5 a, with a gasthat is provided by a movement generating device 5 c in the form of alongitudinally extending gas generator. The gas generator is coupled,corresponding to FIGS. 10, 11 and 15 to 17, to a control unit S and to asensor unit S′ to activate the cooling device 5.

The movement generating device 5 c has a longitudinal axis that runsparallel to the plane of extent of the flange 75 of the diffuser 70 andis aligned with the second end section 81 of the reservoir 5 a. Themovement generating device 5 c is separated from the reservoir 5 amerely by the piston 20, and has a casing that is connected to the wallof the reservoir 5 a and that is likewise aligned with the second endsection 81 of the reservoir 5 a. In this way, the cooling device 5 thatis shown in FIG. 18 forms a compact unit that can be fixed as a separatesub-module to an encircling flange 75 of a diffuser 70.

FIG. 19 shows, in kPa, the pressure (gas sack internal pressure)prevailing in the gas sack 2 of the type shown in FIGS. 1 and 2, as afunction of the cooling liquid quantity (in grams) introduced into theinterior space I of the gas sack 2, for three different volumes of theinterior space I of the gas sack 2. According to the exemplaryembodiment shown in FIG. 19, pressures for 120 liters (dotted line), 60liters (continuous line) and for 30 liters (dashed line) are shown. Ascan be gathered from the illustration, the relationship between the gassack internal pressure and the introduced cooling liquid isapproximately linear.

The priority application, German Patent Application No. 10 2006 010953.8, filed Mar. 3, 2006 including the specification, drawings, claimsand abstract, is incorporated herein by reference in its entirety.

Given the disclosure of the present invention, one versed in the artwould appreciate that there may be other embodiments and modificationswithin the scope and spirit of the invention. Accordingly, allmodifications attainable by one versed in the art from the presentdisclosure within the scope and spirit of the present invention are tobe included as further embodiments of the present invention. The scopeof the present invention is to be defined as set forth in the followingclaims.

1. An airbag module for a motor vehicle, comprising: a gas sack that canbe inflated with gas to protect an occupant; a gas generator forgenerating the gas provided for inflating the gas sack; and anadditional cooling device including: an openable reservoir for storing acoolant for cooling the gas in the gas sack, with the reservoir designedto be opened irrespective of the time of activation of the gasgenerator, so that the coolant can come into contact with the gas, and amovement generating device that opens the reservoir to release thecoolant, wherein the movement generating device provides an overpressurein the reservoir.
 2. The airbag module as claimed in claim 1, whereinthe movement generating device opens a closure of an outflow opening ofthe reservoir, through which the coolant can be released.
 3. The airbagmodule as claimed in claim 2, wherein the movement generating deviceprovides an overpressure in the reservoir that causes a release of thecoolant through the outflow opening of the reservoir when the outflowopening is open.
 4. The airbag module as claimed in claim 2, wherein themovement generating device acts on the closure with a pressure to openthe closure of the outflow opening.
 5. The airbag module as claimed inclaim 2, wherein the closure is formed in one piece with the reservoir.6. The airbag module as claimed in claim 2, wherein the closure isadhesively bonded or welded to the outflow opening.
 7. The airbag moduleas claimed in claim 2, wherein the closure is embodied as a film thatcovers the outflow opening.
 8. The airbag module as claimed in claim 2,wherein the outflow opening of the reservoir divides the coolant into aplurality of droplets when released through the outflow opening.
 9. Theairbag module as claimed in claim 1, wherein before the activation ofthe movement generating device the coolant is enclosed in a destructiblecovering in the form of a diaphragm.
 10. The airbag module as claimed inclaim 9, wherein the cooling device acts on the coolant with a gas viathe diaphragm.
 11. The airbag module as claimed in claim 9, wherein themovement generating device pyrotechnically generates the gas forpressurizing the coolant.
 12. The airbag module as claimed in claim 1,including a piston for pressurizing the coolant.
 13. The airbag moduleas claimed in claim 12, wherein the cooling device acts on the pistonwith a gas to pressurize the coolant.
 14. The airbag module as claimedin claim 12, wherein the piston is mounted with a rotatable threaded barsuch that the piston can, by rotation of the threaded bar, be movedcontinuously in a reciprocating fashion between a first position and asecond position, with the pressure of the coolant in the reservoirincreasing as the piston moves from the first into the second position.15. The airbag module as claimed in claim 14, wherein the movement ofthe piston is generated by the movement generating device.
 16. Theairbag module as claimed in claim 1, wherein the cooling device dividesthe coolant into a plurality of droplets when released.